Gunbus 410 Cubic Inch V-Twin Motorcycle Completed

The Gunbus 410 cubic inch V-Twin motorcycle is complete. The monster engine placed in a motorcycle frame of comparable size looked impossible and many who saw the photos were skeptical of the bike ever being finished but I guess, Clemens F. Leonhardt is one of those persistent guys who ignores the naysayers and keeps at his work.

The fuel injected, 45 degree 6728 cc / 410 cubic inch V-Twin runs through a 3 speed transmission with reverse and actually looks pretty good in its finished state compared to the initial photos, in fact, everything looks good. It puts out 523 foot pounds of torque. Seat height is 31.5 inches and overall length is 136 inches. It is a little heavy at 1433 pounds so high speed corner carving might be an issue and there aren't any photos of the big bike on the road so I guess we'll have to wait for the road test, that is if someone can actually road test this monster.

This is actually going to go into limited series production and a sidecar will be available as well which might help with balance when waiting at a light. I don't even want to think about a driveway tipover. I think this is great! Now, where's the video?

Because he wanted to, because he wondered if it would work, because he thought it was a neat idea, because he wanted to do something different, because he wanted to showcase his engineering skills, because he saw an engine and wondered “what if …,” because he would rather build something himself than watch someone else build something, …, the reasons are endless and every one is valid.

The girl in the pix is probably a pro model, those women are every bit of 5’10” on average… she looks like a midget on that bike!
side car definatel would help, but I cant stop thinking of a trike it!
Are those AIRPLANE tires???

pretty dang awesome. Look what he has to show for all the extra time on his hands. It’s better than a beer gut and couch potato butt.
I couldn’t imagine trying to keep the thing balanced even while under way.
Maybe Batman can buy it to scale down from his existing bike.

lostinoz: I believe Clemens’s original idea was indeed to use tires originally spec’d for a Boeing 767, although I think I also read somewhere that he ended up giving up on that idea because of issues getting wheels to fit, or because he couldn’t get the tread shoulders shaved down to a proper height, or something. I have no idea if the tires on there now are aircraft tires or not, but I’m pretty sure that was the original idea.

so how would you turn the thing? if our model is indeed 5’10, she is leaned forward with her arms locked. with the bars mounted as they are, I’d assume the bars to be prone to “tiller” type steering (swinging left and right rather than pivoting one forward, one back)… ok, now try this out – lean forward, stick your arms straight out and try turning them about an imaginary pivot 4 feet away. it seems like I only have a few degrees lock-to-lock – anyone out there think otherwise, or feel you could conrtol a bike with this layout?

I can’t help but feel that he shouldn’t have scaled the bike up, and instead given it a Hot Wheels, cartoony caricature feel. However, it’s one heck of an amazing build. I’d love to hear this thing at the drag strip.

That is nice work , impractical and silly but I’ve never let that stop me before so I like it. The wheels look over size even for the size of that frame though. It is fun to play with the scale of things so even if it doesn’t really work as a bike it works as a way to throw your small/far away filter and most of us enjoy a little harmless trickery. What would be cool would be to turn the engine through 90deg. like a Guzzi. Now if we worry about where to put the petrol later could we mount that in a “normal bike frame” like a GS1000 or something with each cylinder coming up to allow you to burn your elbows on them during riding. The petrol can now go under the seat. I’m just stuck for a gearbox position.

It weighs twice as much as the average v twin cruiser, but has four times the displacement and almost six times the torque of a Harley twin cam 96 (92 ft/lb according to Motorcyclist). By that measure the Gunbus is a relative featherweight. I always thought cruisers were overweight. Now I know.

Whit that much torque i would like to see how holds up the chain.
36 years ago I got one of the firsts HONDA 750 CB FOUR and man, didi I think It was huge .!Looks like a dwarf next to this . Impressive.

I think its a regular sized bike and he just figured out a way to shrink his girlfriend to make it look huge. An odd name, Gunbus, but a motorcycle but a pretty neat engineering exercise. And no, I don’t think I’ll be adding my name to the pre-order list.

Worth of praise this piece of craftwork, skills, imagination, hard work are easy to see …but honestly my first thought when I saw the article was..
..look what happens when your first girlfriend says ” size does matter” .

There was a day when an odd fellow named Henry Ford, made a very odd thing called an automobile.
It’s certain it recieved a great deal of doubters then.
Today, autos are a part of daily life;
good to see someone take the path less taken.

Ah , Ok , it’s radical ,it’s cool . but is bigger always better ?
I now the girls think so ,like the dream girl in the pix . but you can’t do it with that monster can you .
But A for effort . now downsize to something driveable like boss hoss and you could probably find people who would like to own one .
you’ll be richer for your efforts .
Anyways enjoyed your build . I’d like to hear it running also …. and watch the smoke show !

I vote to call it “The Mangler” as stated above. This THING looks like a man-eater. The front sprocket is just begging to catch a pantleg or a boot strap, having the foot peg right next to it. Primary drive no better, like having a buzz-saw at your knees. How about balance? Yea, just try to stop it from crushing your leg when it catches a gust of wind at a stop light and falls over on you. You surely won’t be able to foot-check a 1400+ lb bike when you skid on that patch of gravel. I view this thing as an oddity no different to the giant drivable shopping cart, or the giant drivable Red Wagon… cool at first glimps, tiring after first minute. Why do people do this? Oh, because you can, that makes it relevant… NOT!

Devildog: you asked, “Why do people do this?” I refer you and all others wondering the same, to kneeslider’s response: “Because he wanted to, because he wondered if it would work, because he thought it was a neat idea, because he wanted to do something different, because he wanted to showcase his engineering skills, because he saw an engine and wondered “what if …” because he would rather build something himself than watch someone else build something, …, the reasons are endless and every one is valid.”

To ” James W ” post #43 : I think you’re mistaken H.F with Herr.Benz, in some place (England?) his creation was deemed so dangerous that the law required a walking guy with a horn to announce the incoming “carriage”.
My post (#42) means: This is rather for the Proof of Concept, Concept model, Kirsch Art section, like most of the beautiful chopper crafts, or my never patented high heel roller blades.
About “Does size matter? visit this link of a guy who also successfully makes bikes:

Testosterone wars. Boss Hoss and this thing. You shouldn’t need a crane to pick up your bike. Now you got something to jump monster trucks with. What will they come up with next? Too much time and loose change. I guess if you got it…….

Dammmit. …. It was enivitable for some retards to come up with things like “stupid” “dumbest thing” etc.
Im convinced that everyone who had a negative thing to say. . .

a)Still lives with his/her parents
b)Has no sustainable job
c)Is “the dumbest thing”
d)Is stupid
e)Is married to “the dumbest thing” or “stupid” who probably weighs the same as the Gunbus
f)Has never even ridden a bike
g)All of the above

Awesome! I’ll volunteer to drive it in a heart beat. I believe handling will not be a problem. Think about how a huge 200kg bike all of a suden becomes very stable once you get going above 10kph. Conversly a tiny 60kg scooter type thing always feels wobbly and unpredictable. My guess is that once it gets going it will be very stable. Stopping will be another issue. Cruising however will be awesome.

around 20 years ago a guy in Australia made a 5 litre v twin supercharged with nitrous oxide injection motorcycle. He made it from the middle two cylinders of a rolls royce merlin aircraft engine. the supercharger and nitrous kit were factory fitted to the motor when used as an airplane in ww2. 3 speed air assisted shift chain drive.
He took it to the usa to compete in sled hauling comps at the bike shows but was banned cause he won em all

After a friend at work forwarded me an email about this I read through all the comments and noticed that only two people actually realized what they were looking at and what they were thinking. My response to the rest of you along with the designer/builder of this “Monstrosity” is “ARE YOU STONED?? Were you one of those little kids that stood at the window eating pant chips all the time? If you still don’t have any idea what I’m talking about drop the can of spray paint and Google the Phrase: (The Death of Common Sense) and have someone read it to you. Yes, if necessary have that person draw pictures for you. I’m thinking that this will be tested on the TV series “Testee’s” or the new series coming out called “1000 Ways to Kill Yourself”. Clemens F. Leonhardt, The next Howard Hughes?

That bike is so stupid, I LOVE IT!! Huge cudo’s for pulling that off. Let’s see the old ladies turn left in front of that beast! It needs a monster trike kit, and a train horn, and I’ll get another mortgage to buy one. Probably have to license it as a truck.

It looks to me he used aircraft cylinders then built the crankcase and crankshaft to match. Great idea.
Many years ago I had the “what if idea” and built a sand buggy that had a Mercury outboard motor with a snowmobile torque converter with a homemade forward and reverse reduction gearbox. Ran it at Yuma, AZ sand dunes back in the early 70s.
Jerry C

The thought of wanting to make something exclusive is fine; but something like this which is doomed to stay parked in a garage or w/e, is honestly, very sad. Common, this is a bike multiplied scale wise, obviously you can build one. But you need to perhaps multiply your physical dimensions in that ratio too, to ride the darn thing. As disappointed i’m to say this, but, WHAT A WASTE ! Poor Sod.

PS i think this is very ridable, just a matter of keeping power on and leaning it into the corners. Don’t see a problem so long as it’s balanced. (which i’m sure it is)
i’ll ride it just to prove it.
MetalMicky

I’m sure its rideable just like every other bike – counter-steering moves the tyre contact patch to one side of the centre of gravity and around it goes. No worries.
But, stopping and not falling over is a whole new ball game where’s the retractable undercarriage. At least his gearbox runs at engine speed (to cope with the torque). Shame he didnt use a hydraulic drive – that WOULD be different infinitely variable ratios and and quite possibly no less efficient than a gearbox.

Awsome .But maybe unridable as noted.I have a partly completed road bike powered by a354 cu in Chrysler Hemi V8.Constructed by the late John Curtin who made Ford 390 V8 in Southwards Museum.I would be intrested in selling it if anyone would be intrested.The rego is on hold.Contact by Email.

I am a little worried about the price for tires for this thing when they wear out, that is of course after riding it around with tow trucks on either side to help keep it upright. Maybe it would be best to let it sit in the living room.

Myself I ride a Honda Rune it can be some what of a challenge to ride at times being that its in the big bike category but truly not as monstrous as the gunbus 410,WOW !This bike would be something I would like to take around the block. Rob S.

The cylinders look like they are from a Wright-Cyclone 1820 Cubic.Inch nine cylinder radial aircraft engine. Aluminum Heads / Steel barrel. Gotta be a real thumper at Idle.
A real challenge to stay upright at the stop light.

Very nice. I have a mockup of something similar and is more efficient. Jay would like mine, too. It’s also an older design than this, so I thought about scaling up right at the first. Great minds think alike, and all that.

Jay Moore,
As I work with radial aircraft engines, I too studied the pics. They are not Curtis Wright, (cast heads) or Pratt & Whitney. (forged heads w/ cut fins) They are probably German. The bore size 176 mm (6.929″) is not found in American radials.
I applaud Herr Leonhardt for his vision and craftsmanship, although I have some critiques; aside from what has already been written.
1) I do not see a starter and battery. This is major. Consider the forces involved on that aspect alone. If you can’t start it, you can’t ride it. It must be self contained.
2) His website promises electronic fuel injection, yet I see no sensors, anywhere. Fuel injection is complex, the plumbing is bulky (especially for this volume demand), and has a lot of components that are difficult to hide. This is something I am currently dealing with for a client’s 142″ injected bike.
3) The general layout. The bike does not have to be so big just because the engine is. Motorcycle chassis design these days include many proven concepts that are ignored here. For example, girder front ends were discontinued ages ago for good reason.

All that being said, I would love to meet this man. I’m working on a 312 project myself.
Jim Flowerjim@jimflowerllc.com

Oops,
Correction to above post: the bore size is 156mm, (6.142″) Not found in American radial engines that I am aware of. The fins closely resemble the Pratt & Whitney R2800 front cylinder head, an Alcoa forging with cut fins. However, the bore size is 5.750″, with a 6″ stroke.
He’s got a cool engine. I would put it in a better chassis though
(With a starter!).
Jim Flower
jimflowerllc.com

The motorcycle is quite beautiful, although I don’t like the yellow color on the tires. I think it may need a sidecar for the potential rollover problems sitting at a light. Field of view in front is a problem. Only a very tall rider could see well enough. I could see this as a trike.

I was “lucky” enough to sit on this bike at the Motobeurs, in Utrecht, The Netherlands. I tell ya, i cannot imagine, how can somebody ride this beast. On a straight line, probably possible, but to steer… Nice to have one, but why? Impossible to use, and you need to build a triple garage to store the bike.

he built it becuse people say it cant be done and its stupid and its a wast of time and money . but i say good job man i would love to own it and hell yes i would ride it too just to prove to people i can lol any way cool bike man keep making things people say you cant. its fun to prove people wrong i do it all the time i have built several things that people said wouldnt work but you know what thay where wrong lol.